Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".

The problem is that Mac OS' (10.11) Finder preview will only show a completely black file while Lightroom shows the correct file contents. On the other side, a TIFF with 3 channels, exported from Lightroom will appear correctly in preview.

Now I create a cropped TIFF from both files, from the original 4-channel and the 3-channel TIFF:

Many viewers will not display CMYK TIFF well unless there is a color profile imbedded. Is your original TIFF CMYKA or was it RGBA. When you remove the alpha it will leave the area under the alpha with the way the input was created. Often that means that those pixels were color/alpha, that is they were not the nominal black/alpha.

Typically at least with RGBA, when I want to remove the alpha, I set the alpha background to black first, like

It seems that Mac OS' Finder cannot deal with large TIFFs (in my case > 5000x3000) that are LZW compressed. The "enfuse" utility creating the original file produced an LZW compressed 4-channel 16-bit TIFF (despite called with --compression=none) which is a bad choice. identify -verbose is very helpful finding such issues.